Diodes ZLNB2015 - Manual (Page 2)

ZLNB2015
ZLNB2015
Document number: DS32061 Rev. 1 - 2
2 of 7
www.diodes.com
January 2010
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Device Description
The ZLNB2015 dual polarization and tone switch controller is
one of a wide range of satellite receiver LNB support circuits
available from Diodes Incorporated. It features two
completely independent channels, each providing logic
outputs to control LNB polarization selection, local oscillator
selection and downfeed disable. It is intended use is in
American voltage and tone controlled LNBs as well as high
performance Twin, Quad and multiple feed Universal type
LNBs, replacing many discrete components to save both
manufacturing cost and PCB size whilst improving reliability.
The ZLNB2015 has been designed to be compatible in low
power consumption LNBs so to improve efficiency it
operates from a single supply of 3V to 8V and has a
quiescent current typically of only 2mA. The quiescent
current does not change significantly with load or logic state.
The two highly accurate polarization control inputs of the
ZLNB2015 have a nominal threshold of 14.25V and to meet
the required demanding needs of broadcasters they have a
guaranteed threshold range of 14.0V to 14.5V. The threshold
is temperature compensated to minimize drift and it also has
a high rejection against the tone signal making the detector
very accurate without the need of further external filtering.
Each features a low and stable input current that enables
transient protection to be achieved with the addition of only a
single resistor per channel. Multi Feed LNBs can be called to
operate with one or more of their controlling receivers
powered down or disconnected, with attendant cable
mismatch problems. To ease design for this situation, each polarization input of the
ZLNB2015 has a second threshold set at a nominal of 8V. An
input voltage below this threshold indicates “receiver not
present”, and switches the relevant Ena output low. This logic
output can be used to disable the associated downfeed driver,
eliminating any problems due to cable mismatch.
Universal LNB local oscillator selection is achieved by
detection of a low level AC voltage superimposed on the
polarization control voltage. To facilitate this function, the
ZLNB2015 includes a separate tone detector for each
channel. Control of detector bandwidth and sensitivity is
provided using an external resistor and capacitor for each
channel. The tone detector has been designed give excellent
rejection of low frequency control signals and DiSEqC™ tone
bursts. The ZLNB2015 has been specifically designed to
minimize the solution cost whilst being flexible. The
ZLNB2015 only requires two external components per
channel to give full user control and functionality. The
ZLNB2015 also includes complimentary outputs so that it can
directly drive many multiplexer ICs without the need of
inverters. Any unused outputs can be left open circuit without
any effect to the remaining circuits operation polarization
switch and tone detector outputs can directly drive TTL and
CMOS logic, pin diodes, IF-amp supply switching and
multiplexer ICs.